Input apparatuses which detect a proximate operation or a touch operation (including a slide operation) by an input body, such as a user's finger, with a sensor and input the operation-based information to an electronic device and the like (for example, a transparent touch panel provided on the front surface of a display panel such as a liquid crystal display panel or the like, and an operation panel in which buttons, switches, keys, pads and the like for operating a variety of apparatuses such as home appliances, mobile phones, personal computers, automobiles and the like are disposed) are known.
As a sensor that detects a proximate operation or a touch operation by an input body, an electrostatic capacitance-type sensor which has a substrate, an electrode provided on the surface of the substrate, a protective layer that protects the electrode, and an external control unit that is connected to the electrode, and detects a variation in the electrostatic capacitance generated between the input body and the electrode, which is caused by a proximate operation or a touch operation by an input body made of a conductor (a user's finger, a movable electrode or the like), with the control unit is known (PTL 1).
Meanwhile, in an ordinary operation panel in which mechanical buttons, switches and the like are disposed, there is a case in which a decorative layer, which is visible from the surface, is provided in order to provide design properties. Examples of the decorative layer include a metal plate and the like.
However, in an operation panel having an electrostatic capacitance-type sensor, in a case in which a decorative layer made of a metal plate is provided in the electrostatic capacitance-type sensor, due to the conductivity of the decorative layer, the variation amount of the electrostatic capacitance between an input body and the electrode decreases, and the detection accuracy of a proximate operation or a touch operation degrades.
Therefore, it is proposed to configure the decorative layer using a fine metal, such as indium, tin or aluminum, in a discontinuous island structure (PTL 2). Since the conductivity of the decorative layer is decreased by configuring the decorative layer in a discontinuous island structure, a decrease in the variation amount of the electrostatic capacitance caused between an input body and the electrode through a proximate operation or a touch operation by the input body is suppressed.
However, in a decorative layer configured in a discontinuous island structure, due to abrasion, compressive stress and the like caused by handling in a manufacturing process, some islands are connected to each other, and form a network which serves as a favorable conductor such that the conductivity is liable to increase. Therefore, it is necessary to confirm the bridging action of all islands, which requires efforts. In addition, tin or aluminum is liable to become an oxide or a chloride, and loses the metal luster over time. Meanwhile, indium is not stably supplied and is expensive.